The decomposition of Malmquist productivity indexes

Two different Malmquist productivity indexes have been proposed. One I call partially oriented because it is either output- or input-oriented, and the other is simultaneously output- and input-oriented. The partially oriented Malmquist index owes some of its popularity to the fact that it has been decomposed to isolate various sources of productivity change. Conversely, the simultaneously oriented Malmquist index has not achieved popularity in part because it has not been decomposed. In this paper I evaluate alternative decompositions of the partially oriented Malmquist index, and I obtain a new decomposition of the simultaneously oriented Malmquist index. This new decomposition leads me to conclude that the latter index is deserving of greater attention than it has received to date.